1. Field of the Invention
The present invention relates to a portable pressure measuring apparatus for detecting a designated altitude by sensing an outside pressure, and more particularly to a portable pressure measuring apparatus for detecting a designated altitude by using pressure data so that a high time resolution is obtained.
2. Description of the Prior Art
As a conventional portable pressure measuring apparatus, there is known a wristwatch with an altitude measurement function. FIG. 5 is a block diagram showing a schematic structure of a conventional wristwatch with an altitude measurement function. The conventional wristwatch with the altitude measurement function includes a pressure sensor 501 for sensing an outside pressure, that is, an atmospheric pressure, an A/D conversion portion 502 for generating digital pressure data by performing A/D (analog/digital) conversion of sensor output (sensing result) of the pressure sensor 501, a calculation portion 503 for calculating altitude data corresponding to the pressure data generated in the A/D conversion portion 502, a measurement control portion 504 for controlling the pressure sensor 501 and the A/D conversion portion 502, a control portion 505 for controlling the whole of the wristwatch with the altitude measurement function, a switch input portion 506 by which a user makes input, a display portion 507 for making display, and a storage portion 508 for storing data.
The storage portion 508 stores altitude data of a designated altitude as a threshold, and the control portion 505 compares the altitude data calculated by the calculation portion 503 with the altitude data stored in the storage portion 508 to detect the designated altitude. In the case where the designated altitude is detected, the control portion 505 gives an alarm.
In the above structure, the operation of the conventional wristwatch with the altitude measurement function will be described with reference to FIGS. 6, 7 and 8. FIG. 6 is a flowchart showing the flow of normal altitude measurement processing in the conventional wristwatch with the altitude measurement function. In the normal altitude measurement processing of the conventional wristwatch with the altitude measurement function, first, the control portion 505 drives the pressure sensor 501 through the measurement control portion 504 to sense the outside pressure (step S601). Subsequently, the A/D conversion portion 502 makes A/D conversion of sensor output of the pressure sensor 501 to generate pressure data (step S602). Next, the calculation portion 503 inputs the pressure data from the A/D conversion portion 502 and calculates altitude data corresponding to the input pressure data (step S603). The control portion 505 inputs the altitude data from the calculation portion 503 and causes the display portion 507 to display the altitude (step S604). Here, a pressure value may be displayed, or the pressure data or the altitude data calculated in the calculation portion 503 may be stored in the storage portion 508.
Next, the process for setting of a threshold altitude will be described. In the case where there occurs an input for setting a measurement value of an altitude as a threshold, or there occurs an input for setting a threshold by a user""s direct designation of an altitude, the setting processing of the threshold is started. FIG. 7 is a flowchart showing the flow of the process for setting of a threshold altitude in the conventional wristwatch with the altitude measurement function. In the setting processing of the threshold in the conventional wristwatch with the altitude measurement function, first, the control portion 505 judges whether there occurred an input for setting a measurement value of an altitude as a threshold through the switch input portion 506 (step S701).
In the case where the input for setting the measurement value of the altitude as the threshold was made, the control portion 505 drives the pressure sensor 501 to sense an outside pressure (step S702), the A/D conversion portion 502 makes A/D conversion of sensor output of the pressure sensor 501 to generate pressure data (step S703), and the calculation portion 503 calculates altitude data from the pressure data generated in the A/D conversion portion 502 (step S704). On the other hand, in the case where it is judged, at step S701, that the input for setting the measurement value of the altitude as the threshold was not made, altitude data is input through the switch input portion 506 (step S706). The control portion 505 causes the storage portion 508 to store the altitude data calculated in the calculation portion 503 or the altitude data input through the switch input portion 506 as the threshold (step S705).
Next, detection processing of an altitude will be described. In the case where there occurs an input of instructions to start detection processing through the switch input portion 506, the detection processing of the altitude is started. FIG. 8 is a flowchart showing the flow of the detection processing of the altitude in the conventional wristwatch with the altitude measurement function. In the detection processing of the altitude in the conventional wristwatch with the altitude measurement function, first, the control portion 505 drives the pressure sensor 501 to sense the outside pressure (step S801), the A/D conversion portion 502 makes A/D conversion of sensor output of the pressure sensor 501 to generate pressure data (step S802), and the calculation portion 503 calculates altitude data from the pressure data generated in the A/D conversion portion 502 (step S803). The control portion 505 inputs the altitude data calculated in the calculation means 503, and displays the altitude through the display portion 507 (step S804).
Next, the control portion 505 compares the altitude data calculated in the calculation portion 503 with the altitude data stored in the storage portion 508, and judges whether the calculated altitude data exceeds the stored altitude data, that is, whether the difference between the calculated altitude data and the stored altitude data is changed from a positive to a negative or from a negative to a positive (S805). In the case where the altitude data calculated in the calculation portion 503 does not exceed the altitude data stored in the storage portion 508, the processing returns to step S801. In the case where the altitude data calculated in the calculation portion 503 exceeds the altitude data stored in the storage portion 508, it is judged that the designated altitude is detected and the processing is ended.
Here, in a time required for the detection processing of the altitude, the ratio of a calculation time for calculating the altitude data at step S803 is large, and a time resolution of the altitude detection, that is, a measurement period in which the steps from step S801 to step S805 are repeated mainly depends on the calculation time of step S803. Thus, calculation processing capacity to a certain extent is required. If a clock frequency of the conventional wristwatch with the altitude measurement function is a clock frequency (several tens of kHz to several MHz) of a general portable apparatus, the time resolution of the altitude detection become s about several hundred ms.
As described above, according to the conventional portable pressure measuring apparatus, the designated altitude is detected by comparing the previously stored altitude data of the designated altitude with the altitude data calculated from the pressure data corresponding to the outside pressure.
However, according to the foregoing conventional technique, since the calculation time for determining altitude is long and the time resolution of the altitude detection is coarse, in the case where it is used in an application in which the altitude changes at a high speed, for example, gliding on skis, skydiving, or the like, which requires a time resolution of about 100 ms to 10 ms, a time delay in the altitude detection can not be neglected, and there has been a problem in that suitable altitude detection can not be achieved.
The present invention has been made in view of the above, and an object thereof is to lessen a time delay in altitude detection and to enable suitable altitude detection.
In order to achieve the above object, according to a portable pressure measuring apparatus of the invention, in the portable pressure measuring apparatus for detecting a designated altitude by sensing an outside pressure, in order to enable the operation of altitude data calculation to be omitted in altitude detection processing (detection processing of an altitude), there are provided generation means for generating pressure data corresponding to the outside pressure, storage means for storing pressure data corresponding to the designated altitude, and detection means for detecting the designated altitude by comparing the pressure data generated in the generation means with the pressure data stored in the storage means. Here, if display of the pressure and altitude is omitted, a time of display processing can be further saved.
Besides, it is also permissible to provide input means for inputting the designated altitude, and pressure data calculation means for calculating pressure data corresponding to the designated altitude inputted through the input means and for storing it in the storage means, so that the designated altitude can be directly set. Besides, it is also permissible to provide input means for inputting instructions to set an altitude where the apparatus itself is positioned as the designated altitude, and pressure data setting means for storing pressure data generated in the generation means as the pressure data corresponding to the designated altitude into the storage means in the case where input is made through the input means, so that the altitude where the apparatus itself is positioned can be set as the designated altitude.
Moreover, it is also permissible to provide generated pressure data, storage means for storing the pressure data generated in the generation means, and altitude data calculation means for calculating altitude data on the basis of the pressure data stored in the generated pressure data storage means, so that a change in altitude during altitude detection processing can be confirmed after the altitude detection processing is ended. Besides, in addition to the altitude, the depth of water may be detected.